Introduction &
The Physics of Sound
Before we can understand how the brain hears (Psychoacoustics), we must master the physical stimulus itself (Acoustics). Today, we build sound from the ground up.
Learning Outcomes
After this lecture, you will be able to:
- Define inertia and elasticity as the two prerequisites for vibration and explain how they produce Simple Harmonic Motion (SHM)
- Describe the equation x(t) = A sin(ωt + φ), identifying each parameter and its physical meaning
- Differentiate between particle displacement and acoustic pressure, applying the principle that the wave travels but the particle does not
- Define condensation and rarefaction as the mechanism by which sound propagates through air
1. The Prerequisites
Define the two fundamental physical properties required for any object to vibrate: Inertia (Mass) and Elasticity (Stiffness).
2. Simple Harmonic Motion
Explain the "atom" of acoustics. We will derive the math behind the sine wave using a mass-spring system as our model.
3. Motion vs. Propagation
Differentiate between particle motion (local oscillation) and wave propagation (energy travel). "The wave travels; the particle does not."
4. Acoustic Pressure
Define sound as a pressure fluctuation \( p \) riding on top of the static ambient pressure \( P_0 \). This is the variable our ears detect.